1. Field of the Invention
This invention relates to thermal ink jet printing systems and, more particularly, to means for sealing the interface between the printheads and their ink supply sources in a reliable, cost effective manner.
2. Description of Prior Art
Thermal ink jet printing systems use thermal energy selectively produced by resistors located in capillary filled ink channels near channel terminating nozzles or orifices to vaporize momentarily the ink and form bubbles on demand. Each temporary bubble expels an ink droplet and propels it towards a recording medium. The printing system may be incorporated in either a carriage type printer or a pagewidth type printer. The carriage type printer generally has a relatively small printhead, containing the ink channels and nozzles. The printhead is usually sealingly attached to a disposable ink supply cartridge and the combined printhead and cartridge assembly is reciprocated to print one swath of information at a time on a stationarily held recording medium, such as paper. After the swath is printed, the paper is stepped a distance equal to the height of the printed swath, so that the next printed swath will be contiguous therewith. The procedure is repeated until the entire page is printed. For an example of a cartridge type printer, refer to U.S. Pat. No. 4,571,599 to Rezanka. In contrast, the pagewidth printer has a stationary printhead having a length equal to or greater than the width of the paper. The paper is continually moved past the pagewidth printhead in a direction normal to the printhead length and at a constant speed during the printing process. Refer to U.S. Pat. No. 4,463,359 to Ayata et al, especially FIGS. 17 and 20 therein, and copending U.S. application Ser. No. 280,104 entitled "Fabricating Process for Large Array Semiconductive Devices", filed Dec. 5, 1988, and assigned to the same assignee as the present invention for examples of pagewidth thermal ink jet printing systems.
U.S. Pat. No. Re. 32,572 to Hawkins et al discloses a thermal ink jet printhead and method of fabrication. In this case, a plurality of printheads may be concurrently fabricated by forming a plurality of sets of heating elements with their individual addressing electrodes on one substrate, generally a silicon wafer, and etching corresponding sets of channel grooves with a common recess for each set of grooves in another silicon wafer. The wafer and substrate are aligned and bonded together so that each channel has a heating element. The individual printheads are obtained by milling away the unwanted silicon material to expose the addressing electrode terminals and then dicing the substrate to form separate printheads.
U.S. Pat. No. 4,638,337 to Torpey et al discloses an improved printhead of the type disclosed in the patent to Hawkins et al wherein the bubble generating resistors are located in recesses to prevent lateral movement of the bubbles through the nozzles and thus preventing sudden release of vaporized ink to the atmosphere.
U.S. Pat. No. 4,678,529 to Drake et al discloses a method of bonding the ink jet printhead channel plate and heater plates together by a process which provides the desired uniform thickness of adhesive on the mating surfaces and prevents the flow of adhesive into the fluid passageways.
U.S. Pat. No. 4,567,493 to Ikeda et al and U.S. Pat. No. 4,577,202 to Hara disclose a liquid jet recording head, including a plurality of protection layers, one of which has a region that directly contacts the liquid. A principal function of the protection layer is to prevent penetration by the liquid and therefore prevent a failure mode for the bubble generating resistors and their addressing electrodes. Hara discloses in FIG. 2b a tubing connection 220 and the patent to Ikeda et al omits details of the ink supply interface.
At present, there is a problem of reliably and cost effectively sealing the thermal ink jet printheads to their ink supplies, whether they are integrally mounted to disposable ink supply cartridges or permanent pagewidth types. None of the above prior art printheads provide a satisfactory solution to this problem.